I do not know of any instrumentation that can see inside the wire at diameters less than 1/10 inches.

Fortunately central burst failures are very rare in common metal (copper and aluminum) drawing practice. One of the indications you get on the surface of the conductor is chevroning which is often called "Crows Feet" which actually describes what the chevrons look like. Please see this web site for more information:
books.google.ca/books?id=YXp6zao0HqgC&pg...%20in%20wire&f=false

Thus there may be chevrons on the surface of your wire when central bursting occurs. The chevrons point in the direction that the wire was drawn. Thus you may be able to see the chevrons on the surface of the wire. The other indication of central bursting is that; "If you bend a piece of central burst wire between your fingers, it usually breaks like a dry twig."

Presumably central burst failures are very rare for you as well. If this is true, I very much doubt that you really need on-line scanning instruments. ( I of course know nothing of the drawing process and drawing failures in platinum Iridium wire but I am assuming that the wire drawing problems are similar. I am also assuming that there was no internal defects in the platinum Iridium to start with Before it was drawn).